1. Field of the Invention
The present invention relates to a data communication system including a data carrier driving apparatus and a data carrier apparatus, and in particular to data communication between the data carrier driving apparatus and the data carrier apparatus.
2. Description of the Related Art
Japanese Patent No. 4393351 describes an example of a configuration that, in a system in which a data carrier driving apparatus and a data carrier apparatus perform data communication, enables bidirectional data communication via two contacts for the purpose of downsizing the system. In order to further improve the versatility of the data carrier apparatus in the data communication system described in Japanese Patent No. 4393351, a generous-purpose microcomputer and a highly-functional memory chip may be used in a circuit in the data carrier apparatus.
However, the above conventional technique has the following problem. When a microcomputer and a highly-functional memory chip are used in a circuit in a data carrier apparatus, this circuit shall be configured using discrete components; this could possibly restrict the space for arranging components in realization of a small data carrier apparatus. In view of this, to avoid an increase in the size of the data carrier apparatus, a rectification smoothing circuit, which can be implemented with a small number of components, may be used as a voltage generation circuit in the data carrier apparatus. That is to say, a voltage is obtained by rectifying and smoothing a clock pulse signal supplied from a data carrier driving apparatus using the rectification smoothing circuit in the data carrier apparatus, and the obtained voltage is used as a power supply voltage for the microcomputer and the memory chip.
When the rectification smoothing circuit is used in the data carrier apparatus as a circuit for generating a power supply voltage, the size of the data carrier apparatus can be kept small. However, if a peak value of a charging current increases during an operation for charging a capacitor (capacitance element) used in the rectification smoothing circuit, a relatively large current could possibly flow from the data carrier driving apparatus to the data carrier apparatus. This could possibly lead to a temporary decrease in the level of a clock pulse signal (pulse voltage) supplied from the data carrier driving apparatus to the data carrier apparatus, and a decrease in the detection accuracy for the clock pulse signal in the data carrier apparatus. As a result, there is a possibility that stable data communication is difficult to perform between the data carrier driving apparatus and the data carrier apparatus.